This invention relates to power transmission and steering systems for vehicles and more particularly to a friction disc drive for vehicles capable of small radius turns.
It is highly desirable in certain types of vehicles, such as lawn mowers, tractors and lift trucks, to permit very small or zero radius turns. In lawn mowers, for example, sharp turns are required to maneuver the vehicle as it traverses back and forth across the area to be cut and maneuvers around obstructions. One type of drive for vehicles such as lawn mowers which permit sharp turning is disclosed in U.S. Pat. No. 3,616,869. In particular, this patent discloses a hydraulically driven vehicle, such as a lawn mower, having a pair of drive wheels, each of which is independently operated by an individual pump coupled to the vehicle's engine. Each pump includes a control lever for regulating flow direction and fluid pressure to each motor. This permits the drive wheels to be independently rotated in selected forward and reverse speeds whereby the mower may be driven either forwardly or in reverse and may be turned through any desired angle. Another type of hydraulically driven lawn mower employs a single pump and valves for controlling flow direction and pressure. While hydraulic lawn mowers have many attractive aspects, the required hydraulic components, such as pumps, motors and valves, tend to be relatively expensive. For this reason, there is a need for a zero radius turn drive for lawn mowers and other vehicles which do not require expense hydraulic components.